Electronic equipment is often assembled from subassemblies of electronic components on printed circuit boards (PCBs) that receive power and communicate through a common bus. In some implementations of this architecture, power is delivered through a bus to individual boards at a voltage that is directly usable by the loads on those boards. Recent trends in electronic equipment architecture include the use of higher voltage buses in conjunction with DC—DC power conversion at the board level. Thus, for example, a bus operating at 48 volts delivers power to an on-board power converter having a lower output voltage, such as 3.5 volts, for use by devices on that board. The implementation of an architecture having a higher voltage bus is facilitated by the use of preassembled DC—DC power conversion modules (power modules) that are adapted for mounting on a PCB, and have pins to provide electrical connections between a module and a PCB.
Power modules are commonly mounted parallel to a PCB at a predetermined stand-off distance to accommodate PCB and power module components and to allow for cooling air to flow around heat generating components. Connecting terminal pins typically span the stand-off distance between the power module and PCB, and usually protrude through holes in the power module and PCB, where electrical connections are made. In addition to providing the proper electrical connections, the mounting of power conversion modules on PCBs must also provide for the physical support of the power module on the PCB, and this support structure should not impede the cooling of heat dissipating components on the power module or the PCB. Due to the weight of the power module and the small diameter of standard terminal pins, some provision is also usually made to physically support the combined power module/PCB structure.
One prior art system for connecting power modules with PCBs is illustrated in FIGS. 1 and 2. FIG. 1 is a perspective view of a power conversion module 110 having a plurality of pins 100, and FIG. 2 is a sectional view of the power module 110 and pins 100 as mounted on a PCB 120. Power module 110 includes a board 111 having a first side 113 with electronic components C, a second side 115, and a plurality of holes 112 through the module. Each of the plurality of pins 100 passes through one of holes 112 and is electrically connected to conductive traces (not shown) on board 111. Specifically, holes 112 are adjacent to conductive traces on board 111, with electrical connections between board 111 and pins 100 provided typically by solder 131. In general, conductive traces may be present on either side of board 111, and/or in interior layers of board 111, and thus pins 100 may be soldered on one or both sides of board 111, as required.
Typically, a PCB having power requirements is configured for accepting a particular power module 110 including terminal pins 100. PCB 120 has a first side 121 and a second side 123, and a plurality of holes 125 positioned in a predetermined conventional fashion with respect to conductive traces (not shown). Holes 125 are positioned to accept pins 100 according to the position and required voltages at each one of holes 125. Thus, PCB 120 is configured to accept module 110 by having holes 125 that match the pattern of holes 112, and by having conductive traces on the PCB that can accept and provide the appropriate signals through pins 100. With pins 100 placed through holes 125, electrical connections are made using solder as shown at 133. Pins 100 have a length sufficient to allow module 110 and PCB 120 to have a stand-off distance S as shown in FIG. 2. The plurality of pins 100 thus span the stand-off distance S, protrude through mounting holes 112 and 125, and are electrically attached to the conductive traces by solder 131 and 133.
Pins 100 are long, cylindrical members, and as such do not provide sufficient physical support to the combined power module 110 and PCB 120 structure to prevent movement of the assembled components. To provide a more rigid structure, surface mounted supports 117 having a height S for connecting second side 115 of module 110 and first side 121 of PCB 120 are provided, as shown in FIGS. 1 and 2. Supports 117 can be tubular or boxlike structures, preferably of metal, as shown in FIGS. 1 and 2, or can be solid stand-off supports. The addition of several supports 117 provides support to maintain module 110 and PCB 120 at the predefined stand-off distance S, as well as provide rigidity to prevent the power module and PCB from moving relative to one another, for example, as might occur as a result of movement of the electronic equipment in which they are assembled. While the prior art device of FIGS. 1 and 2 can provide the required electrical connections and physical support for module 110 and PCB 120, there are several drawbacks. One drawback is that supports 117 must be fabricated and attached to module 110 and PCB 120. This adds to the complexity and cost of the assembly. Another drawback is that supports 117 occupy valuable surface area on the respective assemblies. In addition, the current carrying capability of pins 100 is limited by pin diameter, which is the diameter of holes 112 and 125.
FIG. 3 shows another prior art device that attempts to overcome some of the previously noted deficiencies by combining the electrical and mechanical functions of the pin and support structures into a prior art pin 300. Specifically, FIG. 3 shows a sectional view of prior art terminal pin 300 adapted for connecting a module 310 to a PCB 320. Module 310 has a board 311 with a first side 315 and holes 312. PCB 320 has holes 325 and an opposing side 321 at a stand-off distance S. Each pin 300 has a first end 301, a second end 303, and a central portion 305 with a first flange 307 and a second flange 309. The flanges 307 and 309 abut surfaces 315 and 321, respectively, providing structural support for maintaining module 310 and PCB 320 at the predetermined stand-off distance S. Similar to the prior art pin of FIGS. 1 and 2, module 310 includes pins 300, and the module and pin combination is attached to PCB 320 using solder. Board 311 and PCB 320 have electrical traces (not shown) adjacent to holes 312 and 325, respectively, as in the prior art device of FIGS. 1 and 2. Electrical contacts between pins 300 and module 310 and PCB 320 are provided by solder 331 and 333. The distance between flanges 307 and 309 is equal to the stand-off distance S, and thus each pin 300 provides both an electrical connection between module 310 and PCB 320 and physical support to both the module and PCB. Module 310 and PCB 320 can be assembled with pins 300 alone, or by the combination of pins and supports, such as supports 117.
While each pin 300 provides an electrical connection as well as physical support, this pin makes it difficult to provide adequate electrical contact between the module 310 and PCB 320. Thus, for example, there is a close fit between each of the pins 300 and the corresponding hole 325 and between the flange 309 and the surface of module 310. As a result, during the soldering step, the flow of solder 331 and 333 between each pin and the PCB is hindered, and thus it is difficult to provide a good electrical connection between the pins 300 and the PCB.
What is needed is an improved pin for mounting a module to a PCB that provides electrical and physical support. Specifically, there is a need for pins having reduced electrical and thermal resistance. There is also a need for pins that provide increased bending resistance to increase the rigidity of connected components, and a need to provide for improved soldering capabilities. Such a pin should be compatible with standard PCB assembly techniques.